It's time for an update. The technologies continue to explode faster than they can be applied. New systems are continually introduced. Systems incorporate ever-greater functionalities and capabilities, blurring layers of control and definitions. Mergers, acquisitions, new players and dropouts have altered the vendor lineup. The expanding lexicon of acronyms and abbreviations continues to confuse. And the Internet is changing everything, raising premature expectations of "e-commerce" yet opening real opportunities for supplier/customer collaboration.
Microsoft standards have been implemented for process control "because they're pervasive in the enterprise," observes John Blanchard, principal analyst at the ARC Advisory Group (Dedham, MA). "The enterprise wants business data in the form it's been using at the business level -- that's what pushed MS standards into the control system."
This may be partly due to the ever-increasing functionalites offered by today's plant-floor process control systems. As reported earlier by FE (March, '01), supervisory control and data acquisition (SCADA) has become more difficult to define as these systems add more production-management and manufacturing-execution functions, blurring the distinction between SCADA and MES (Manufacturing Execution Systems). A typical SCADA system integrates PLCs with a PC. Today, that integration increasingly includes HMI (human/machine interface), a PC with graphic process and machine-status displays, alarms., messages, diagnostics, database access, reporting tools and automated process execution, allowing operator feedback.
Major vendors now call these systems HMI/SCADA, and their latest releases incorporate the Microsoft DNA-M standards cited earlier plus Web portals for integrating via Internet across the enterprise using XML, and accessible via Web browser from "thin clients" anywhere in the enterprise. As reported by Kevin Prouty, reearch director for manufacturing strategies at AMR Research (Boston), "the Web is transforming automation systems without engineers knowing it. When engineers weren't looking, companies like Rockwell Automation and Schneider Electric slipped Web servers into their PLCs." As reported last month by FE, the latest HMI/SCADA systems from Wonderware, Intellution, National Instruments, Citect and Camstar also incorporate Web portals accessible by thin clients via Web browser. Systems integrators who can mix-and-match software to customize control and information systems to the user's specific needs are becoming more important than ever.
Integration via Internet will enable close collaboration between manufacturers and customers to eventually achieve that elusive goal of Efficient Consumer Response (ECR). But trusting relationships and integration with well-developed customer standards must evolve before food manufacturers can truly collaborate with retail and food-service across the supply chain, said William R. Friend, retired vice-president of the J.R. Simplot Food Group, at Food Engineering's Food Automation 2001 conference last February in Fort Lauderdale, Fla. In the absence of trust, however, collaborative forecasting and production-planning will be driven by:
Every day, the plant requires five truckloads of sugar, 13 truckloads of flour, 300 pallets of fruit and 178 pallets of margarine, so scheduling batches and tracking ingredient use is critical. A multilayered control system engineered by EMTROL, Inc. automates batching, handling and delivery of dough to the pie lines, as well as filling operations. EMTROL supplied the dough-handling system, its control software, validated the system through computer simulations before installation, and assisted with systems integration.
The system integrates an EMTROL Automated Trough System (ATS), EMTROL PIMS (Production Information and Management System) software, a Microsoft SQL server database, 20 Allen-Bradley PLCs, five cell controllers and 11 operator-interface stations running Rockwell RSView32 software, 13 Allen-Bradley PanelView operator terminals and 13 barcode readers.
The ATS is a laser-guided, PLC-controlled closed-loop automated storage and retrieval system situated between the four dough mixers and elevated conveyors which carry the dough to dumper stations at the head of each pie line. A stacker crane moves horizontally between two rows of storage racks capable of holding more than 300 loaded and empty custom-designed stainless-steel troughs on six levels. A transfer vehicle with two-trough capacity delivers filled dough troughs to a shuttle vehicle carried on the stacker crane. Together, crane and shuttle deliver troughs to designated rack positions and record each trough's "address" with a barcode scanner. The trough remains at its designated location for several hours as part of a retarding process which improves the flaky texture of the dough. When dough in a given trough is ready, the trough is retrieved and moved to an elevated conveyor supplying one of the pie lines.
PIMS orchestrates the entire dough-delivery and pie-filling process including dynamic scheduling to ensure a constant supply of dough and filling to the pie lines; rack-positioning troughs for maximum throughput with minimal handling; and moving individual troughs throughout the system. The ATS communicates with cell controllers via the plant's Ethernet, and executes one mission every minute.
Integrated batch control
To start the process, the mixer cell controller queries the database to determine if a batch is scheduled. If so, batch information is downloaded from the database, and converted into recipe and ingredient instructions by RSView32 and transmitted to the Shick ingredient-delivery system and mixer controllers.
The Shick system feeds ingredients into four high-volume San Cassiano mixers. When a mix is complete, the mixer signals the ATS to deliver a trough. The mixer dumps a batch of dough weighing up to 1,000 lbs. into a trough; the trough is scanned for identity; moved through two stations where the dough is compressed and the trough is lidded, and the trough is delivered to the rack system as a new empty is dispatched to a mixer.
When a trough is retrieved from the rack system, the ATS delivers it to an EMTROL dumper, where it is scanned to assure identity and dumped onto an elevated belt conveyor supplying one of the pie-shell molding machines. After dumping, the trough is weighed to confirm that it's empty, then either returned to staging or routed at pre-set time intervals to washing and drying stations. Meanwhile, PIMS also controls the fruit and custard-cooking and filling processes. Along the way, RSView32 HMI stations allow operators to monitor the process and make changes when necessary.
EMTROL, Inc., 3050 Hempland Road, Lancaster, PA 17601. Phone: (717) 397-2531; Fax: (717) 393-7230; Website: www.emtrol.com
Rockwell Automation, 1201 South Second St.,Milwaukee, WI 53201. Phone: (414) 382-2000; Fax: (414) 382-4444; Website: www.rockwellautomation.com